The food sector is always looking for a substitute for a saccharose which is too calorific. In this respect a Limburg business company believes it has discovered it in the form of tagatose. To produce it in industrial quantities it has appealed to the ULg’s Centre for Protein Engineering, which has worked on a particularly effective and profitable enzyme for sugar production: cold lactase.

Whilst sugar (saccharose) is presented by its producers as the most minor of major pleasures, it is also one of the major factors within a series of health problems hitting our society hard, such as obesity. Replacing saccharose with a less calorific substance has thus become one of the priority objectives of the food sector, which is launching onto the market more and more diet products with the aim of people getting back or simply maintaining their figure and improving our health. The market in sweeteners has developed considerably in recent years, with a regular batch of controversies, notably as far one of the best known of them, aspartamine, is concerned. That is why agro-food companies are permanently looking for a natural substitute for saccharose which has the taste of sugar, the appearance of sugar and the texture of sugar, but without the calories. The Limburg firm Nutrilab appears to have found it in the form of tagatose. What remains is to produce it on an industrial scale. And that is where the ULg’s Centre for Protein Engineering (CPI) comes in.

A cold enzyme

‘Nutrilab contacted us in the month of May 200,  following work which we had published on an enzyme which originates in the Antarctic,’ explains Jean-Marie François, the project head who, under the management of Moreno Galleni and Bernard Joris, mobilised a team of CPI researchers composed of Etienne Baise, Alain Brans and Michael Delmarcelle. ‘This enzyme comes from a psychrophilic micro-organism (Pseudoalteromonas haloplanktis), in other words it lives in low temperature environments. The enzyme in question is a lactase, which is called, given its origins, a cold lactase.’ Lactase is a pretty widespread enzyme (or a common one) which hydrolyses lactose, a sugar which is primarily found in milk products. It thus breaks down lactose into glucose and galactose, monosaccharides (simple non-hydrolysable sugars) which can subsequently be absorbed by the human body.  The activity of the lactases is very important in new-borns and then diminishes over childhood. This diminishing of lactases – or even its absence in certain populations, notably in Asia – explains in part why certain adults tolerate milk less well. But here it is the role it plays in tagatose production which interests us.

After the hydrolysis of lactose we thus have glucose and galactose. At this stage another enzyme (called isomerase) intervenes and converts galactose into tagatose. Tagatose is thus an isomer of galactose. What sparked Nutrilab’s interest is the fact that lactase can be effective at low temperatures and thus works when milk is preserved in fridges (at temperatures of around 4°C). Moreover an enzymatic reaction is a totally natural reaction which allows chemical procedures also used to extract tagatose from lactose to be replaced. Finally, the use of enzymes should be less expensive than the chemical method of separation. It remained to move from the laboratory to the industrial stage. That is the challenge the CPI team picked up with success.